A. Technical Field
An embodiment disclosed herein is generally directed to a hot stick switch head for securing high-voltage fuses, fuse barrel assemblies, or other similar or related devices during removal and installation.
B. Background Art
The present invention relates to a tool used to remove and replace electrical fuses and/or other related devices commonly used in electrical transmission and distribution systems. As detailed in U.S. Pat. No. 6,725,745 to Palmieri, single-phase and three-phase electrical power is delivered to commercial, industrial, and residential users through a system known as the power distribution grid, which generally includes such components as generating plants, transformers, and electrical power lines. These lines generally consist of both transmission lines, which typically have AC voltages in the range of about 70,000 to about 750,000 volts, and distribution lines, which typically have AC voltages in the range of about 2,300 to about 50,000 volts. Inevitably, there is an element of danger in working with these high voltages, yet there are many instances in which utility workers have to either service or repair these high voltage power lines in the performance of their duties. These service and repair duties often include the replacement of power line fuses, which, when operable, can carry hundreds of amps of electrical current and, even when inoperable, these fuses may be in an energized circuit carrying thousands of volts of electricity, which may still be available at the load side of the fuse.
Generally, power line fuses are located at or near the tops of power poles, which can place these fuses over 30 feet above the surface of the ground, and each fuse is generally carried in a fuse holder commonly referred to as a “fuse barrel assembly,” which is used to provide an interface between the fuse and the fuse block, which is connected to the power line. Generally, the bottom end of the fuse barrel assembly has a hinge assembly that is comprised of an ejection assembly (for “automatically” releasing the top end of a blown fuse from a fuse block) and a pair of pivot pins (one pin on each side of the hinge assembly) that are adapted to fit into slots formed on the bottom of the fuse block. This bottom portion of the fuse block is commonly referred to as a “fuse block saddle.” Generally, the top end of the fuse barrel assembly has a hoop, a pull-ring, or some other similar structure, and the hinge assembly has a slot, and both allow for the insertion of an arm (or bar) portion of a switch head tool through the hoop or slot so that the fuse barrel assembly can be manipulated by the switch head tool. This manipulation or handling of the fuse barrel assembly includes, but is not limited to, carrying the fuse barrel assembly to and from the fuse block saddle, and inserting the top end of the fuse barrel assembly into (and/or removing the top end of the fuse barrel assembly from) the top end of the fuse block, which is commonly referred to as the “fuse block switch.” Briefly stated, the insertion and removal of the fuse barrel assembly from the fuse block switch is accomplished by rotating the top end of the fuse barrel assembly about the pivot point defined by the pivot pins and the slots on the fuse block saddle. In other words, after the hinge assembly is properly seated in the fuse block saddle, the fuse barrel assembly is supported by the fuse block saddle and is free to be rotated about the pivot point. This allows the top end of the fuse barrel assembly to be rotated into the fuse block switch in order to insert the fuse into the electrical circuit that it is a part of, or alternatively the top end of the fuse barrel assembly can be rotated away from the fuse block switch to remove the fuse from its electrical circuit, in which case the fuse tool can be inserted through the hinge assembly slot and used to both lift the fuse barrel assembly from the fuse block saddle, and then carry the fuse barrel assembly to the ground for servicing or replacement.
Oftentimes these fuses have to be replaced during inclement weather conditions including heavy rains and high winds. Generally, the prior art switch heads used for replacing fuses are comprised of fittings attached to insulated extension poles and have one or two prongs, arms, and/or hooks that are used for, among other functions, carrying and manipulating the fuse barrel assembly into, and/or out of, the fuse block. FIG. 1 illustrates a prior art switch head configured with a single extension arm. Many of these prior art switch heads, however, do not have a means for securing a fuse barrel assembly to the switch head while being manipulated. This can lead to the extremely dangerous condition of the fuse barrel assembly becoming separated from the switch head and hurtling a considerable distance to the ground causing serious personal injuries and significant property damage. Moreover, this dangerous condition becomes even more likely during inclement weather conditions.